1. Field of the Invention
The present invention relates to recording paper for ink-jet recording (hereinafter referred to as ink-jet recording paper) of coated-paper type which is useful for recording with an ink-jet recording apparatus, particularly for recording with an ink-jet recording apparatus equipped with a recording head having a plurality of ink-ejection nozzles.
The present invention also relates to an ink-jet recording method employing the above ink-jet recording paper.
2. Related Background Art
The ink-jet recording system, which ejects an ink (recording liquid) directly onto a recording paper sheet, is attracting attention because of its low operation cost and low noise generation.
In recent years, in ink-jet recording, multi-nozzle type recording apparatuses have come to be used for full-color image recording by use of a plurality of color inks at a high recording speed.
For such a recording system, aqueous inks are used in view of safety and printing characteristics of the ink. The recording paper therefor is required to absorb the ink quickly; not to cause running of ink even when different colors of ink dots are overlapped; to allow appropriate ink-dot spreading; to enable formation of ink dots in a shape approximate to a true circle with a sharp dot edge; and naturally to have sufficient whiteness of the recording face in order to obtain high density and high contrast of the dots.
Hitherto, coated paper is used to satisfy the above requirements. However, the coated paper sheet sometimes cockles or wrinkles depending on the environmental conditions.
Japanese Patent Application Laid-Open No. 62-95285 discloses improved cast-coated paper to satisfy the above requirements for the image formation and to prevent the wrinkle formation.
Such recording paper, however, involves various problems when it is used for ink-jet recording with an on-demand type ink-jet apparatus having a multi-nozzle which applies a large amount of ink locally in a short time. If ink absorbency of the recording face is made lower to achieve higher optical density of the recorded image, the applied ink is liable to bleed and preferential absorption of the dyes in the inks is liable to occur to cause color irregularity: for example, black color printing with four color-inks of yellow, cyan, magenta, and black may result in irregular brown colored pattern on a black background (a bronze phenomenon).
If the recording layer is modified to absorb the ink at the surface portion, the ink causes swelling of the surface portion of the recording layer, whereby fine roughness may be caused on the cast-coated surface to lower the gloss at the printed area.
If composition of a coating color for recording layer formation is changed to raise the ink absorbency of the recording layer, another problem of drop of optical density of the print arises, although the above surface roughness formation is prevented.
The cast-coated paper sheet can be made resistant to cockling and wrinkling by increasing the thickness of the paper sheet to utilize the inherent rigidity of the paper. However, in the on-demand type ink-jet recording system employing a multi-nozzle with the increased thickness of the recording paper, the ink absorption is completed at the portion of printed side without penetration of the ink into the interior of the recording paper sheet, and if the printing is practiced on the entire surface of the recording paper, the printed face side of the paper shrinks as a whole to cause significant curling with the printed face concaved.